Tensions have flared up in Northern Ireland as protests by nationalist elements turn more violent with police officials promising widespread arrests.

During the third consecutive night of violence in the Catholic majority Ardoyne area in Belfast, nationalist rioters on Tuesday night fired up to six shots at police forces and attacked them with petrol and pipe bombs, AFP reported.

Assistant Chief Constable Duncan MaCausland said children as young as 10 were involved in the violence and were used as shields by "sinister elements."

"There will be significant arrests in the forthcoming days," he added, saying police had hours of video footage that would be used to identify rioters.

On the other hand, UK Prime Minister David Cameron called the violence in Belfast "unacceptable," and charged the protesters with leaving the police with no other option but to respond to the rioting.

Earlier on Monday, a rioter dropped a concrete block on a policewoman which seriously injured her. More than 80 police officers were injured over the previous two nights of rioting by nationalist youths while 55 officers were injured on Monday night alone.

On 12 July, people in Northern Ireland celebrate Orangemen's Day which marks the Glorious Revolution and victory of Protestant King William of Orange over Catholic king James II at the Battle of the Boyne in 1690.